The present invention relates to methods of as well as apparatus and systems for determining temperature conditions of interest within an environment and, more particularly, to methods, apparatus, and systems for determining the magnitude and location of temperature conditions of interest within an environment through the use of effective and reliable electronic means in combination with a suitable array of one or more transducers.
In certain environments, as for example, nuclear reactors, steam or hot water pipes, electrical cable trays, aircraft or marine engines, granaries, manufacturing processes, refrigeration systems, etc., it is often essential to establish and maintain the continuous monitoring of temperature conditions of interest throughout the environment. This may be accomplished in many ways. One of the more common expedients has been to position a plurality of temperature sensors at various selected points within the environment and monitor each of the sensors individually. A more satisfactory system, however, involves the use of what may be called continuous transducers suitably positioned and arranged throughout the environment to be monitored. Such transducers may, in one form or configuration, each comprise at least a pair of thermocouple conductors surrounded by a mass of semiconductive material enclosed in a protective sheath. In this form of construction, the semiconductive material is usually of a composition which exhibits a negative or inverse temperature-resistance characteristic. The thermocouple conductors in such a transducer are formed of dissimilar thermoelectric materials capable of establishing temperature representative thermoelectric voltages when a junction is established therebetween in accordance with the well-known Seebeck effect. When a transducer embodying the aforedescribed construction is exposed to an environment wherein the temperature deviates from ambient, one or more thermoelectric junctions are established between the thermocouple conductors along the length of the transducer at those locations whereat the temperature deviation exists.
Suitable detection means associated with such a transducer can then be utilized to sense a voltage representative of the maximum temperature deviation from ambient existing along the length of the transducer. Suitable constructions of such transducer configurations are disclosed (as well as various alternate forms of suitable transducer constructions), for example, in U.S. Pat. No. 2,805,272, issued Sept. 3, 1975; U.S. Pat. No. 2,764,656, issued Sept. 25, 1956; U.S. Pat. No. 3,205,296, issued Sept. 7, 1965; and U.S. Pat. No. 3,408,607, issued Oct. 29, 1968. Among the techniques that may be advantageously employed to yield such constructions are those disclosed in U.S. Pat. No. 3,533,260, issued Nov. 21, 1967 and U.S. Pat. No. 3,737,997, issued June 12, 1973.
While systems utilizing such transducers can yield an indication of the magnitude of a maximum temperature condition existing along a transducer within a monitored environment, it is also important to have the capability of determining the precise location of such a maximum temperature condition within an environment by automatically initiating a determination of the location of that maximum temperature condition when its value exceeds a preselected minimum value. One system of the latter type is disclosed in U.S. Pat. No. 3,493,949, issued Feb. 3, 1970. In that system (as described more fully in the referenced patent), an energy source is adapted to apply energy to a transducer to establish a voltage drop along that portion of one of the transducer conductors which lies between (a) the point of application of the energy and (b) the junction where the maximum temperature condition prevails. The electronic means employed in such a system includes the capability of measuring the established voltage drop and, preferably, of converting that voltage drop to a direct indication of the location of the maximum temperature condition.
It has also been determined that a system employing a form of bridge network can be utilized for determining both the magnitude and location of temperature conditions. Such a system is disclosed in U.S. Pat. No. 3,683,606, issued Aug. 15, 1972. The measuring and locating functions are accomplished in one preferred form of such a detection system by providing a balanced dual energy source for applying energy to the transducer. The energy source applies energy to selected areas of the thermocouple conductors comprising the transducer and resultant voltage signals are translated into data representative of both the magnitude and location of the temperature condition.
While the foregoing briefly traces several of the earlier advances in the art, there has still not been available methods, apparatus and systems which are readily and effectively capable of continuously (and selectively) monitoring a large number of transducers (e.g., on the order of 300 to 1,000 or more) within an expansive and/or complex environment. Among the advantages to be realized with such a more versatile system configuration is the isolation of those transducers (or portions thereof) which are exposed to preselected temperature conditions of interest. As a concomitant of such isolation of those preselected temperature conditions, means can be provided for generating sense perception signals indicative of maximum temperature conditions and/or indicative of various different temperature levels, including a constantly monitored temperature profile of the environment of interest.